Are you smarter when you write than when you speak? Essayist Arthur Krystal thinks so. Writing is a different process than off-the-cuff speaking. He uses an anecdote about seeing a film of Vladimir Nobokov on a sound stage being interviewed. He had made an impressive reply to an question, but Krystal then noticed that Nobokov was using canned answers from index cards. Krystal says:

Hazlitt...remarked that he did not see why an author “is bound to talk, any more than he is bound to dance, or ride, or fence better than other people. Reading, study, silence, thought are a bad introduction to loquacity.”

Like most writers, I seem to be smarter in print than in person....I’m expressing opinions that I’ve never uttered in conversation and that otherwise might never occur to me.

Krystal also points out that writing is a more deliberate process, which may account for the differences in spoken and written communications. Here is the full New York Times essay on the question: are we smarter when we write?